1) Field of the Invention
The present invention relates to a method and apparatus for spinning bicomponent filaments in a sheath/core polymer configuration. More particularly, the invention relates to a spinneret, used for bicomponent spinning, having a plurality of orifices in a boss.
2) Description of Prior Art
Bicomponent filaments of the sheath/core configuration are well-known and a variety of spinning packs and spinnerets have been employed in the production of such filaments. A conventional spinning assembly involves feeding molten sheath forming material to the spinneret orifices, in a direction perpendicular to the orifices, and injecting molten core forming material into the sheath-forming material as it flows into the spinneret orifices.
As disclosed in U.S. Pat. No. 5,505,889 to Davies, prior art bicomponent spinnerets provide one orifice per boss. Boss spacing, and consequently orifice density, is restricted by a manufacturing requirement of one millimeter spacing between adjacent bosses. An increased orifice density yields a corresponding increase in the number of filaments produced. Accordingly, there is a need for an improved spinneret with an increased orifice density.
The present invention is directed towards a spinneret assembly and method for spinning bicomponent filaments. According to the present invention, the spinneret assembly includes a distributor and a spinneret. The distributor is provided with inner openings near the center of the distributor and with outer openings further from the center. The inner openings convey molten sheath polymer to the spinneret and the outer openings convey molten core polymer to the spinneret. The spinneret is provided with an integral boss having a plurality of orifices for receiving core polymer which coaxially align with the distributor outer openings for receiving core polymer. By providing the spinneret with an integral boss having multiple orifices, orifice density is increased over prior art spinnerets which contain one orifice per boss. Orifices on the same boss can be manufactured closer to each other than orifices on adjacent bosses. The spinneret is also provided with a plurality of openings and recessed pathways adjacent to the boss for conveying sheath polymer to the orifices.
According to another aspect of the present invention, the bosses are curvilinear. Still further aspects of the present invention include spiral, semi-circular or linear bosses.
According to another aspect of the present invention, a method is provided for making a bicomponent filament. The method includes providing a distributor having an inner flow passage and outer flow passages, providing a spinneret beneath the distributor having a plurality of bosses which have a plurality of orifices aligning with the outer flow passages, forcing core polymer through the outer flow passages and the spinneret openings, forcing sheath polymer through the inner flow passage and onto recessed pathways provided adjacent to the boss, and forcing the sheath polymer through the recessed pathways, over the bosses, then through the spinneret openings to form a sheath about the core polymer.